Timing Attack RCE via Remote Secret Comparison in Spring Boot 3.x
CVE-2026-40972 Published on April 27, 2026
An attacker on the same network as the remote application may be able to utilize a timing attack to discover information about the remote secret. In extreme circumstances this could result in the attacker determining the secret and uploading changed classes, thereby achieving remote code execution in the remote application. Affected: Spring Boot 4.0.04.0.5 (fix 4.0.6), 3.5.03.5.13 (fix 3.5.14), 3.4.03.4.15 (fix 3.4.16), 3.3.03.3.18 (fix 3.3.19), 2.7.02.7.32 (fix 2.7.33); DevTools remote secret comparison. Versions that are no longer supported are also affected per vendor advisory.
Vulnerability Analysis
Weakness Type
Observable Timing Discrepancy
Two separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not. In security-relevant contexts, even small variations in timing can be exploited by attackers to indirectly infer certain details about the product's internal operations. For example, in some cryptographic algorithms, attackers can use timing differences to infer certain properties about a private key, making the key easier to guess. Timing discrepancies effectively form a timing side channel.
Products Associated with CVE-2026-40972
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Affected Versions
Spring Boot:- Version 4.0.0 and below 4.0.6 is affected.
- Version 3.5.0 and below 3.5.14 is affected.
- Version 3.4.0 and below 3.4.16 is affected.
- Version 3.3.0 and below 3.3.19 is affected.
- Version 2.7.0 and below 2.7.33 is affected.